Abstract
Structural, magnetic, and optical properties along with N2 absorption-desorption features of Sm3+–Dy3+ ions co-substituted BaSr hexaferrite microspheres (HFMSs) engineered through a hydrothermal gel approach were investigated. The microstructural and morphological features were examined by powder X-ray diffraction (XRD), surface area and pore size distribution (BET), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HR-TEM), and transmission electron microscopy (TEM) techniques. Rietveld analysis proved the purity of products. The BET revealed a slight variation in textural characteristics with increasing Sm3+–Dy3+ substitution. The surface area (11–16 m2/g) exhibits a pore volume of ~0.07 cm3/g and average pore size distributions of 26.6 nm. The 300 K and 10 K field-dependent hysteresis loops were registered. Remanent magnetizations (Mr) and coercive fields (HC) are in a range of 29.15–34.05 emu/g and 1420–5391 Oe at 300 K, respectively. The estimated saturation magnetizations (Ms) vary between 53.22 emu/g and 71.08 emu/g, and magneton numbers (nB) are in a range of 10.51–13.93 μB. At 10 K, the Mr = 35.18–46.83 emu/g, HC = 1487–4760 Oe, Ms = 81.82–99.17 emu/g, and nB = 14.83–19.44 μB, which are greatly higher compared to room temperature. All magnetic parameters exhibit strong ferrimagnetic features of pristine Sr0·5Ba0·5Fe12O19 and Dy3+ and Sm3+ co-doped HFMSs at both temperatures. Squareness ratios (SQRs), which are very close to 0.50 assign the single domain uniaxially symmetric structured HFMSs. δM type of remanence plots was applied to specify the intensity and type of interparticle interactions as a function of the externally magnetic field, H. The Schuster-Kubelka-Munk theory provides to estimate direct energy band gaps (Eg). Undoped or co-doped HFMSs have a very narrow magnitude of Eg data between 1.795 and 1.865 eV depending on the couple ion concentrations.